The invention relates to a static mixing element in a flow channel, the element having at least two deflectors, and to a mixing device having such element. Simple static mixing elements having deflectors are known but their mixing and homogenising abilities are very limited and they always produce a relatively high pressure drop. More elaborate static mixers, for example, comprising crossing subchannels of slats (Sulzer-SMV-mixers) provide very good mixing but are relatively costly to produce. Good mixing is particularly necessary when a small quantity of a fluid is injected by means of an injection system into a main flow of another fluid in a flow channel. When relatively small quantities, for example, of less than 10%, of a gas or a liquid are admixed into the flow of another gas or another liquid, very one mixing paths in the empty tube are necessary to ensure thorough homogeneous mixing. However, conventional mixing devices having complicated adjustable injection systems cannot provide thorough mixing over a wide range of loads and more particularly at very low volume flow relationships. For example, in denoxing installations denitrogenation is performed by admixing gaseous ammonia into the flue gas flow in a very low proportion of from 1 : 1000 to 1 : 10 000; very thorough homogeneity is required, with a maximum deviation of less than 5% from the average value, to ensure that in the subsequent catalyst the reaction of NH3 with NOX proceeds very uniformly everywhere, in order to keep within low nox limits and also to ensure that no surplus ammonia breaks through. The stoichiometric mixing ratios must therefore be maintained uniformly and permanently over the whole channel cross-section. Also, this thorough mixing must be achieved over short paths and with a low pressure drop and known mixing devices cannot provide these two features.
It is therefore the object of this invention, using very simple means, to provide very thorough mixing with a relatively low pressure drop and to provide overall advantages as compared with the known kinds of mixer, and it is another object of the invention to provide by means of the static mixing element a simple mixing device which ensures, with a reduced pressure drop and over short paths, high-quality mixing over the entire channel cross-section and over a wide range of load conditions.